The present invention relates to a method for manufacturing a thin-film magnetic head with at least an inductive writing head element.
A method for manufacturing a thin-film magnetic head with only an inductive writing head element, or a composite type thin-film magnetic head with both an inductive writing head element and a magnetoresistive effect (MR), giant magnetoresistive effect (GMR) or tunneling magnetoresistive effect (TMR) reading head element may include a process of forming a magnetic gap layer on a lower magnetic pole (or an upper shield layer when it is the composite type thin-film magnetic head), a process of forming an upper magnetic pole layer on the magnetic gap layer by frame plating, and a trimming process performed thereafter. In the trimming process, a part of the upper surface of the lower pole layer surrounding the upper pole layer used as an etching mask is dry-etched to make a protruded portion or a pedestal of the lower pole layer. This trimming process aims to make a width PWL of the protruded portion of the lower pole layer (hereinafter also called as a pole width), which opposes the upper pole layer via the gap layer, equal to a width PWU of the upper pole layer (hereinafter also called as a pole width) by dry etching.
The term of xe2x80x9cdry etchingxe2x80x9d executed in this trimming process has broad meaning including ion milling, reactive ion etching (RIE) and other etching. However, in the following description, examples using the ion milling will be explained.
In the conventional fabricating process using such a trimming process, the width PWU of the upper pole layer after the trimming process will not have a constant value along a throat-height (TH) direction. The more the throat height TH increases, the narrower the width PWU becomes.
FIGS. 1a to 1c are plane views schematically illustrating a plane shape of a resist frame and an upper magnetic pole layer seen from the direction of multi-layering when fabricated by the conventional method.
More detail, FIG. 1a represents a plane shape of a resist frame when the upper pole layer is fabricated by using a frame plating method, FIG. 1b represents a plane shape of the upper pole layer formed by the plating, and FIG. 1c represents a plane shape of the upper pole layer after the trimming. It should be noted that these figures indicate the plane shapes around a region where the throat height TH is zero.
In general, a photo-mask used for making a resist frame has the same shape as the resist frame.
As will be noted from the figures, according to the conventional method, the upper pole layer is frame-plated so that its width PWU is kept constant along the throat-height direction. If ion milling is executed using such an upper pole layer as a milling mask, since the upper pole layer itself will be removed not only in its depth direction but also in its width direction and an etching rate will increase as the throat height TH becomes large, the width PW of the upper and lower pole layers becomes gradually small depending upon the change of the etching rate. Since an incoming angle of the ion beam is slanting to the upper pole layer, this ion beam will be shadowed by the level difference of an insulation layer or a yoke located behind the upper pole layer arises. For this reason, the change of the etching rate will occur. The amount of this change of the pole width PW in the throat-height direction depends upon the three-dimensional shape of elements near the zero throat-height position (TH=0), such as the insulation layer and the yoke, or on the conditions of the ion milling.
If the pole width PW varies along with the throat-height direction, in the polishing process for adjusting the throat height (throat-height adjustment process) performed thereafter, a pole end edge width will vary according to the polished amount, and the yield of magnetic head manufacturing will get worse.
It is therefore an object of the present invention to provide a method of manufacturing a thin-film magnetic head, whereby throat-height dependability of a pole width can be eliminated, and thus a pole end edge width can be prevented from varying.
According to the present invention, a method of manufacturing a thin-film magnetic head, includes a first step of forming a second magnetic pole layer (an upper magnetic pole layer) on a magnetic gap layer formed on a first magnetic pole layer (a lower magnetic pole layer) so that the second magnetic pole layer opposes to the first magnetic pole layer via the magnetic gap layer, and a second step of dry etching a part of an upper surface of the first magnetic pole layer surrounding the second magnetic pole layer used as an etching mask to make a width of the dry-etched part of the first magnetic pole layer equal to a width of the second magnetic pole layer. Particularly, according to the present invention, the first step includes shaping at least part of the second magnetic pole layer so that the width of the second magnetic pole layer increases as a throat height becomes large.
At least part of the upper pole layer is formed in a shape that the width of the upper pole layer increases as a throat height becomes large. Thus, even if the upper pole layer itself is partly removed in its width direction to decrease its width, this decrease in the pole width is compensated so that the width of the upper and lower pole layers after the dry etching is kept constant along the throat-height direction. Therefore, in the polishing process for adjusting the throat height performed thereafter, a pole end edge width will not vary according to the machined or polished amount, and thus the yield of magnetic head manufacturing can be prevented from getting worse.
It is preferred that the first step includes shaping the second magnetic pole layer so that the width of the second magnetic pole layer increases from a position of a zero throat-height as the throat height becomes large.
In this case, it is preferred that the width of the second magnetic pole layer continuously, namely linearly or in curve, increases as the throat height becomes large.
In this case, it is also preferred that the width of the second magnetic pole layer discontinuously increases as the throat height becomes large.
It is preferred that the first step includes shaping the second magnetic pole layer so that the width of the second magnetic pole layer increases within a region of the throat height TH=0 to +3 xcexcm as the throat height becomes large.
It is also preferred that the first step includes shaping the second magnetic pole layer so that the width of the second magnetic pole layer is kept constant from a position of a zero throat-height to a predetermined position of a larger throat-height and increases from the predetermined position as the throat height becomes large.
In this case, it is preferred that the width of the second magnetic pole layer continuously, namely linearly or in curve, increases from the predetermined position as the throat height becomes large.
In this case, it is also preferred that the width of the second magnetic pole layer discontinuously increases from the predetermined position as the throat height becomes large.
It is also preferred that the first step includes shaping the second magnetic pole layer so that the width of the second magnetic pole layer increases depending upon a change in etching rate of the dry etching.
It is further preferred that the first step includes shaping the second magnetic pole layer so that the width of the second magnetic pole layer increases depending upon an etching rate near a position of a zero throat-height during the dry etching and upon etching rates at predetermined positions with larger throat heights during the dry etching.
It is preferred that the first step includes shaping the second magnetic pole layer so that the width of the second magnetic pole layer increases depending upon etching rates determined by measuring, after the dry etching, widths of a sample that has a constant width along the throat-height direction before the dry etching.
It is also preferred that the first step includes patterning the second magnetic pole layer by a plating process.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.